WiFi Calling

https://www.jio.com/en-in/jio-wifi-calling

https://www.airtel.in/wifi-calling

https://www.myvi.in/vi-wifi-calling

https://medium.com/@workrockin/what-is-wifi-calling-technology-and-how-does-it-work-in-sync-with-the-cellular-provider-a3efc6c28abb

https://www.republicworld.com/technology-news/mobile/how-to-enable-jio-wifi-calling-on-phones-a-step-by-step-user-guide.html